Method for manufacturing electrode plate having transparent type or reflective type multi-layered conductive film

ABSTRACT

An electrode plate for display device includes a substrate and a multi-layered conductive film. The multi-layered conductive film includes a lower side amorphous oxide layer, a silver-based layer, and an upper side amorphous oxide layer. The lower side amorphous oxide layer and the upper side amorphous oxide layer are formed of an amorphous and amorphous-like material. The film thickness of the upper side amorphous oxide layer is not larger than 20 nm.

BACKGROUND OF THE INVENTION

[0001] This invention relates to an electrode plate which has asubstrate and a multi-layered conductive film and which can be appliedto a reflection preventing film, electromagnetic wave shielding film,transparent type or reflective type electrode for solar battery orelectrode plate for a display device such as a liquid crystal displaydevice or EL (electroluminescence) display device and a method formanufacturing the electrode plate.

[0002] A transparent electrode formed by arranging a transparentconductive film for permitting light of predetermined electrode patternto pass therethrough on a glass substrate, plastic substrate orsubstrate on which semiconductor elements are formed is widely used fordisplay electrodes of various types of display devices such as a liquidcrystal display, an input/output electrode which permits an input to bedirectly effected on the display screen of the display device and thelike.

[0003] As a liquid crystal display device using the transparentelectrode, it is generally to use a transmission type liquid crystaldisplay device containing a light source (lamp) as a back light. In thetransmission type liquid crystal display device, since the powerconsumption by the back light lamp is large and thus the service life isshort in the case of battery driving, the portability which the liquidcrystal display device originally has cannot be fully utilized. For thisreason, at present, a reflective type liquid crystal display deviceusing ambient light (that is, containing no back light lamp) is activelydeveloped.

[0004]FIG. 5 shows a reflective type liquid crystal display device 50which is formed of a reflective type electrode plate 51 and atransparent electrode plate 52 with sandwiching LCD 509. The reflectiveelectrode plate 51 is adhered to the transparent electrode plate 52 viaa seal 510 such that the transparent electrode 507 faces the transparentelectrode 505.

[0005] In the reflective electrode plate 51, a reflection film 502 andcolor filter 503 are sequentially formed on the surface of a backsubstrate 501 comprised of, for example, glass which faces a liquidcrystal 509. A protection layer 504 for protecting and the leveling thesurface of the color filter 503 and a transparent electrode 505 aresequentially formed on the color filter 503.

[0006] On one surface of the transparent plate, such as a glass plate511, a polarizing film 508 is laminated. On the other surface of theglass plate 511, an array of transparent electrode 507 with TFT (thinfilm transistor)s 506 is formed. The color filter 503 is formed ofplural pixels of light transmission type (which are hereinafter simplyreferred to as pixels) colored in R (red), G (green) and B (blue) andarranged in a predetermined pattern. The reflection film 502 is alsoused as a reflection electrode which can be used as a liquid crystaldriving electrode in some cases.

[0007] In the conventional case, a thin aluminum film is widely used asthe reflection film 502 formed on the back substrate 501. This isbecause aluminum is a metal having a large reflectance of light in thevisible region, but recently, it is proposed to use silver as a materialof the reflection film from the viewpoint of enhancement of thereflectance and a problem that a lowering in the reflectance of aluminumdue to contact with the liquid crystal or glass substrate occurs.

[0008] However, the reflectance of silver itself is larger than aluminumby approx. 10%, but it has the following main defects when it is used toform a thin film of the electrode plate.

[0009] First, the adhearability thereof to the substrate of a materialsuch as glass or plastic is low and it is easily separated from thesubstrate when it is formed on the substrate as a thin silver film.Particularly, when an electrode is formed on the substrate such as aglass plate, an SiO₂ film is previously formed on the substrate and asilver-based layer is formed on the SiO₂ film in some cases in order toprevent nebula of silver (or prevent the silver-based layer frombecoming slightly opaque) due to migration of alkali metal from thesubstrate. At this time, since the adhesion between the SiO₂ film andthe silver-series thin film is poor, it is necessary to form an adhesionlayer formed of a thin oxide film between the SiO₂ film and thesilver-series thin film. Therefore, the manufacturing process becomescomplicated and the manufacturing cost is increased.

[0010] Secondly, a silver-series thin film formed of highly pure silveron the substrate tends to aggregate and become opaque by the influenceof heat and oxygen and the reflectance of light tends to be lowered.

[0011] Thirdly, in a case where the thin silver film is exposed and madein direct contact with the outside air, silver sulfide or silver oxideis formed on the surface of the thin silver film and the thin silverfilm becomes discolored and the reflectance thereof is lowered.

[0012] Therefore, as the technique for solving the above problem anddefects, the technique for forming a three-layered conductive filmhaving a thin silver film disposed between oxide layers is proposed inU.S. Pat. No. 5,667,853 by the inventors of this invention.

[0013] In the above proposal, in a case where the transparent electrodefor the transmission type liquid crystal display device is formed by useof the three-layered conductive film, the upper side oxide layer (oxidelayer formed on the upper surface of the thin silver film) is formed inan amorphous state and the upper and lower oxide layers are formed witha slightly large film thickness of approx. 40 nm in order to attain theoptimum optical characteristic. The reason why the upper side oxidelayer is formed in the amorphous state is to prevent that silver atomsmove along the grain boundary when crystals or grains are present in theoxide layer and the silver-based layer is aggregated or becomes opaqueand the reflectance or transmissivity is lowered.

[0014] However, the above proposal has the following problem.

[0015] When the three-layered conductive film of the above proposal ispatterned by the photolithography process by use of an etching solution,contact corrosion due to contact between different types of metalsoccurs, damage due to the etching process (particularly, damage to theinterface between the thin silver film and the oxide film) is large, andparticularly, the upper side oxide layer may be easily separated.

[0016] Further, in order to form a stable amorphous film as the oxidefilm, a mixed oxide layer having different types of oxide materialsmixed together is used in some cases. But in this case, the electricalconnection resistance of the conductive film becomes high and it is notdesirable as the conductive film. Further, as described before, sincedamage to the interface between the thin silver film and the oxide filmoccurs, the reliability such as humidity resistance is greatly loweredand it does not reach the practical level.

BRIEF SUMMARY OF THE INVENTION

[0017] This-invention is made to solve the above problem and an objectof this invention is to provide an electrode plate including atransmission type or reflective type conductive film and having anexcellent optical characteristic (transmittance, reflectance), lowelectrical connection resistance, good patterning configuration and highreliability.

[0018] In the following description, the lower side amorphous oramorphous-like oxide layer is an oxide layer which is one of the oxidelayers holding the silver-based layer therebetween and is formed on thesubstrate before formation of the silver-based layer and the upper sideamorphous or amorphous-like oxide layer and upper side oxide layer areoxide layers laminated on the silver-based layer after formation of thesilver-based layer.

[0019] (1) According to this invention, there is provided an electrodeplate for display device which includes a substrate and a multi-layeredconductive film, the multi-layered conductive film including asilver-based layer, a lower side amorphous oxide layer formed of anamorphous or amorphous-like material for suppressing the movements ofsilver atoms at the interface with the silver-based layer, and an upperside amorphous oxide layer formed of an amorphous or amorphous-likematerial for suppressing the movements of silver atoms at the interfacewith the silver-based layer, the film thickness of at least the upperside amorphous oxide layer being not larger than 20 nm.

[0020] With the above configuration, the upper side amorphous oxidelayer has a function for suppressing the movements of silver atoms atthe interface with the silver-based layer (it practically plays a roleas an anchor for fixing the movements of silver atoms) and can suppressoccurrence of aggregation and slight opaqueness caused by the movementsof silver atoms at high temperatures and a lowering in thetransmissivity or reflectance due to the aggregation and slightopaqueness.

[0021] It is preferable that the upper side amorphous oxide layer is anoxide layer in which the value of an optical film thickness defined asthe product of the film thickness and the refractive index is 20 nm orless.

[0022] With the above configuration, the refractive index of the upperside amorphous oxide layer can be set to a smaller value and thereflectance can be enhanced when the electrode plate is formed as thereflective type.

[0023] The electrode plate for display device has a protection layerformed on the upper side amorphous oxide layer and it is preferable thatthe sum of the optical film thicknesses of the upper side amorphousoxide layer and the protection layer is 70 nm or more. With the aboveconfiguration, the transmissivitys of the upper side amorphous oxidelayer and the protection layer can be enhanced when the electrode plateis formed as the transmission type.

[0024] The electrode plate for display device has a protection layerformed on the upper side amorphous oxide layer. It is preferable thatthe protection layer is formed of an oxide layer having the refractiveindex equal to or smaller than that of the upper side amorphous oxidelayer and it is preferable that the lower side amorphous oxide layer hasan underlaid layer formed of an oxide layer having the refractive indexequal to or smaller than that of the lower side amorphous oxide layer.

[0025] With the above configuration, the refractive indexes of the upperside amorphous oxide layer and the lower side amorphous oxide layer canbe enhanced. As a result, the transmissivity can be further enhancedwhen the electrode plate for display device is formed as thetransmission type.

[0026] It is preferable that the lower side amorphous oxide layer of theelectrode plate for display device is a mixed oxide which containscerium oxide as a main material and additionally contains one or moreoxide materials selected from a group of ytrium oxide, zirconium oxide,niobium oxide, hafnium oxide, tantalum oxide and tungsten oxide.

[0027] With the above configuration, the lower side amorphous oxidelayer has high adhesion with the silver-based layer and has an alkalibarrier effect for preventing migration of alkali metal such as Na fromthe substrate which is a supporting member into the silver-series thinfilm.

[0028] The electrode plate for display device is characterized in thatat least niobium oxide is used as the mixed oxide mixed with the ceriumoxide which is the main material of the lower side amorphous oxidelayer. It is characterized in that the lower side amorphous oxide layeris formed of an amorphous or amorphous-like mixed oxide which containsat least niobium oxide mixed with cerium oxide.

[0029] With the above configuration, the lower side amorphous oxidelayer sufficiently prevents migrations of alkali metal such as Na fromthe substrate into the silver-based layer and of silver atoms to theinterface of silver-series thin film. As a result, the reliability canbe enhanced.

[0030] In the electrode plate for display device, the silver-based layermay be a silver alloy containing at least one metal selected from agroup of platinum, palladium, gold, copper and nickel added to silver by3 at % (atomic percentage) or less.

[0031] A conventional multi-layered film is added to silver by largerthan 3 at % (atomic percentage). However, with the above configuration,since the silver-based layer is held between the upper side amorphousoxide layer and the lower side amorphous oxide layer, the substrate canbe stably carried in the manufacturing process such as thephotolithography process and a protection layer can be formed afterformation of the pattern. As a result, an additive amount of an alloyelement added to silver can be suppressed to minimum and the performanceof the conductive film can be further enhanced.

[0032] (2) According to this invention, there is provided an electrodeplate for display device which includes a substrate and a multi-layeredconductive film, the multi-layered conductive film including a lowerside amorphous oxide layer formed of an amorphous or amorphous-likematerial for suppressing the movements of silver atoms at the interfacewith the silver-based layer, a silver-based layer, and an upper sideoxide layer, the upper side oxide layer including an oxide layer and anamorphous oxide layer formed of an amorphous or amorphous-like materialfor suppressing the movements of silver atoms at the interface with thesilver-based layer and the film thickness of the upper side amorphousoxide layer being not larger than 20 nm.

[0033] With the above configuration, the upper side oxide layer and thelower side amorphous oxide layer have a function for suppressing themovement of silver atoms at the interface with the silver-based layer(it practically plays a role as an anchor for fixing the movements ofsilver atoms) and can suppress occurrence of aggregation and slightopaqueness caused by the movements of silver atoms at high temperaturesand a lowering in the transmissivity or reflectance due to theaggregation and slight opaqueness.

[0034] It is preferable that the value of an optical film thicknessdefined as a product of the film thickness and a refractive index of theamorphous oxide layer included in the upper side oxide layer is notlarger than 20 nm or less.

[0035] With the above configuration, the refractive index of theamorphous oxide layer can be lowered and the reflectance can be enhancedwhen the electrode plate is formed as the reflective type.

[0036] It is preferable that the electrode plate for display device hasa protection layer formed on the upper side oxide layer and the sum ofthe optical film thicknesses of the upper side oxide layer and theprotection layer is 70 nm or more.

[0037] With the above configuration, the transmissivitys of the upperside oxide layer and the protection layer can be enhanced when theelectrode plate is formed as the transmission type.

[0038] The electrode plate for display device has a protection layerformed on the upper side oxide layer and it is preferable that theprotection layer is an oxide layer having the refractive index equal toor smaller than that of the amorphous oxide layer and it is preferablethat the lower side amorphous oxide layer has an underlaid layer formedof an oxide layer having the refractive index equal to or smaller thanthat of the lower amorphous oxide layer.

[0039] With the above configuration, the refractive indexes of theamorphous oxide layer and the lower side amorphous oxide layer can beenhanced, and as a result, the transmissivity can be further enhancedwhen the electrode plate for display device is formed as thetransmission type.

[0040] It is preferable that the lower side amorphous oxide layer of theelectrode plate for display device is formed of a mixed oxide whichcontains cerium oxide as a main material and additionally contains oneor more oxide materials selected from a group of ytrium oxide, zirconiumoxide, niobium oxide, hafnium oxide, tantalum oxide and tungsten oxide.

[0041] With the above configuration, the lower side oxide layer has highadhesion with the silver-series thin film and has an alkali barriereffect for preventing migration of an alkali metal such as Na from thesubstrate which is a supporting member into the silver-series thin film.

[0042] The electrode plate for display device is characterized in thatat least niobium oxide is used as the mixed oxide added to the ceriumoxide which is the main material of the lower side amorphous oxidelayer. It is characterized in that the lower side amorphous oxide layeris formed of an amorphous or amorphous-like mixed oxide which containsat least niobium oxide mixed with cerium oxide.

[0043] With the above configuration, the lower side oxide layersufficiently prevents migration of alkali metal such as Na from thesubstrate and of silver to the interface of silver-series thin film. Asa result, the reliability can be enhanced.

[0044] The electrode plate for display device is characterized in thatthe silver-based layer may be formed of a silver alloy containing atleast one metal selected from a group of platinum, palladium, gold,copper and nickel added to silver by 3 at % (atomic percentage) or less.

[0045] A conventional multi-layered conductive film has more than 3 at %materials added to silver to stabilize the movement of silver. Howeverwith the above configuration, since the silver-based layer is heldbetween the lower side amorphous oxide layer and the upper sideamorphous oxide layer, the substrate is not affected by themanufacturing process such as the photolithography process and thus aprotection layer can be formed after formation of the pattern. As aresult, an additive amount of an alloy element added to silver can besuppressed to minimum and the performance of the conductive film can befurther enhanced.

[0046] (3) According to this invention, there is provided a method formanufacturing an electrode plate for display device comprising thefollowing steps of forming a multi-layered conductive film on asubstrate, the multi-layered conductive film comprising a lower sideamorphous oxide formed of amorphous or an amorphous-like oxide, an upperside amorphous oxide formed of an amorphous or amorphous-like oxide anda silver-based layer which held between the lower side amorphous oxidelayer and the upper side amorphous oxide layer, a film thickness of theupper side amorphous oxide layer being not larger than 20 nm; forming anelectrode by patterning the oxide layers together with the silver-basedlayer and forming a protection layer on the electrode, a film thicknessof the protection layer being adjusted to attain an optimum opticalcharacteristic as the electrode.

[0047] According to this invention, there is provided a method formanufacturing an electrode plate for display device comprising thefollowing steps forming a lower amorphous oxide layer formed of anamorphous or amorphous-like material forming a silver-based layer on thelower amorphous oxide layer and forming an upper amorphous oxide layerformed of an amorphous or amorphous-like material and having a filmthickness not larger than 20 nm on the silver-based layer.

[0048] With the above configuration, since the photolithography processcan be effected when the conductive film is formed in a predeterminedelectrode pattern, the etching process can be easily effected, no damageto the interface portion between the amorphous oxide layer and thesilver-based layer due to the etching process occurs and the patterningprocess can be effected with high precision.

[0049] In the method for manufacturing the electrode plate for displaydevice, it is preferable that the step of forming the protection layeris a step of forming the protection layer made of an electricalinsulating material on the electrode with a sufficiently large filmthickness for protection in a portion other than the electricalconnection portion of the electrode.

[0050] With the above configuration, since the protection layer has anelectrically insulating property, the electrical short circuit betweenthe facing substrates can be prevented. Therefore, the abnormaloperation due to the electrical short circuit can be prevented.

[0051] In the method for manufacturing the electrode plate for displaydevice, it is preferable that the pattern processing step of effectingthe patterning process is a photolithography method using a photoresist,the resist in the electrode portion for electrical connection is leftbehind when the photoresist is selectively removed after the electrodepattern is formed in the process of the photolithography method, and theresist left behind is used as a mask for forming the protection layer,then the resist is removed to expose the electrode portion forelectrical connection from the protection layer. Further, it ispreferable that the pattern processing step of effecting the patterningprocess is a mask sputtering method.

[0052] With the above configuration, if the photolithography methodusing the photoresist is used as the method for selectively forming theprotection layer on the electrode plate, selection with the highprecision can be attained and a manufacturing method suitable for ahighly precise pattern of a liquid crystal display device or the likecan be attained, and if the mask sputtering method is used, theprotection layer can be easily formed with a precision slightly lowerthan that of the photolithography method and a manufacturing methodsuitable for a relatively rough pattern of a solar battery or the likecan be attained.

[0053] Additional objects and advantages of the present invention willbe set forth in the description which follows, and in part will beobvious from the description, or may be learned by practice of thepresent invention.

[0054] The objects and advantages of the present invention may berealized and obtained by means of the instrumentalities and combinationsparticularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0055] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate presently preferredembodiments of the present invention and, together with the generaldescription given above and the detailed description of the preferredembodiments given below, serve to explain the principles of the presentinvention in which:

[0056]FIG. 1 is a view showing the schematic structure of an electrodeplate according to a first embodiment of this invention;

[0057]FIG. 2 is a view showing the schematic structure of an electrodeplate according to a second embodiment of this invention;

[0058]FIG. 3 is a view showing the schematic structure of an electrodeplate according to a third embodiment of this invention;

[0059]FIG. 4 is a view showing the schematic structure of an electrodeplate according to fourth and fifth embodiments of this invention; and

[0060]FIG. 5 is a view showing the schematic structure of a conventionalreflective type liquid crystal display device.

DETAILED DESCRIPTION OF THE INVENTION

[0061] There will now be described first to fifth embodiments of thisinvention with reference to the accompanying drawings.

[0062] In the electrode plate for display device according to thisinvention, the silver-based layer included in a multi-layered conductivefilm forms a preferable reflection electrode when the film thickness ofthe silver-based layer is set to approx. 100 to 200 nm or more and formsa preferable transparent electrode when the film thickness of thesilver-based layer is set in a range of approx. 7 to 25 nm.

First Embodiment

[0063]FIG. 1 is a view showing the schematic structure of an electrodeplate according to a first embodiment of this invention.

[0064] In FIG. 1, the main portion of an electrode plate 9 according tothe first embodiment is constructed by a glass substrate 10 (made byCorning Co. 1737 material) with a thickness of 0.7 mm and an underlaidlayer 1 with a thickness of 29 nm, a lower side amorphous oxide layer 2with a thickness of 10 nm (as will be seen later, the lower sideamorphous oxide function as a lower side anchoring layer), asilver-based layer 3 with a thickness of 15 nm, an upper side amorphousoxide layer 4 with a thickness of 10 nm (as will be seen later, theupper side amorphous oxide function as an upper side anchoring layer)and a protection layer 5 with a thickness of 29 nm which aresequentially laminated on the glass substrate 10. The lower sideamorphous oxide layer 2, thin silver-based layer 3, and upper sideamorphous oxide layer 4 form a multi-layered conductive film.

[0065] In the above configuration, if the glass substrate 10 is a sodaglass substrate, the underlaid layer 1 has a function of an alkalibarrier effect. Further, if an adherence between a substrate and anoxide layer is weak, the underlaid layer 1 has also a function ofadherence layer for adhering between the substrate and the oxide.

[0066] The electrode plate 9 according to the first embodiment is alight transmission type electrode plate since the film thickness of thesilver-based layer 3 is 15 nm (which lies in a range of approx. 7 to 25nm).

[0067] The electrode plate 9 according to the first embodiment is formedby the following manufacturing process.

[0068] That is, first, the glass plate 10 which has been cleaned isinserted into a vacuum chamber (sputtering chamber) and a vacuum isdrawn.

[0069] Next, the underlaid layer 1 is laminated and formed on the glassplate 10 by the sputtering method.

[0070] Then, the glass plate 10 is taken out from the vacuum chamber(sputtering chamber) and is heated at 300° C. for one hour to besubjected an anneal process. The glass plate 10 is again inserted intothe vacuum chamber (sputtering chamber) and a vacuum is drawn. The lowerside amorphous oxide layer 2, silver-based layer 3, and upper sideamorphous oxide layer 4 are sequentially laminated and formed on theunderlaid layer 1 by the sputtering method.

[0071] Then, the resultant glass plate 10 is taken out from the vacuumchamber (sputtering chamber) and a resist pattern (not shown) having apredetermined pattern (for example, stripe pattern) is formed on theupper side oxide layer 4 by the photolithography process. Next, sulfuricacid-series etchant containing nitric acid and iron nitrate by 1 weight% is used as an etching solution to simultaneously remove portions ofthe three layers of the lower side amorphous oxide layer 2, thesilver-based layer 3 and the upper side amorphous oxide layer 4 whichlie in an exposed portion from the resist pattern by etching.

[0072] Next, after a resist pattern portion corresponding to a displayplane 16 shown in FIG. 1 is exposed again (at this time, a terminalportion 17 is not exposed), the resist pattern portion in the portion ofthe display plane 16 is removed by use of an organic alkali solution.

[0073] Next, the protection layer 5 is formed on the entire surface ofthe glass substrate 10 by use of the sputtering chamber.

[0074] Then, after the substrate is exposed again, the resist patternlying on the terminal portion 17 is removed by use of the organic alkalisolution, and then, the anneal process (heat treatment) for heating thesubstrate at the temperature of 200° C. for one hour is effected toobtain the electrode plate 9 of the first embodiment.

[0075] In the above manufacturing process, the underlaid layer 1 andprotection layer 5 are each formed by use of a sputtering target formedof a mixed oxide material containing tin oxide, cerium oxide and galliumoxide. The composition of the sputtering target included tin 80 at %(atomic percentage), cerium 10 at % (atomic percentage) and gallium 10at % (atomic percentage) in terms of the atomic percentage of metalelements (an oxygen element is not counted).

[0076] Next, the lower side amorphous oxide layer 2 and upper side oxidelayer 4 are each formed by use of a sputtering target formed of a mixedoxide material containing indium oxide, cerium oxide, tin oxide andtitanium oxide and the composition of the sputtering target includedindium 88 at %, cerium 8.5 at %, tin 3 at % and titanium 0.5 at % interms of the atomic percentage of metal elements (an oxygen element isnot counted).

[0077] Further, the composition of an alloy target used for forming thesilver-series thin film 3 included silver 98.5 at %, gold 1 at % andcopper 0.5 at %.

[0078] The inventors of this invention formed films to a film thicknessof 100 nm by use of the same materials as the protection layer 5 (or theunderlaid layer 1) and the lower side amorphous oxide layer 2 (or theupper side amorphous oxide layer 4) and measured the refractive indexesof the films. As the result, it was understood that the refractive indexof the former film was 2.06 and the refractive index of the latter filmwas 2.10 at the wavelength of 550 nm.

[0079] The sum of the optical film thickness (the product of the filmthickness and the refractive index) of the protection layer 5 (or theunderlaid layer 1) with a film thickness of 29 nm and the optical filmthickness of the upper side oxide layer 4 (or the lower side amorphousoxide layer 2) was (29×2.06+10×2.17)=(59.74+21.0)=80.74 nm.

[0080] Under the above optical characteristics, it was confirmed thatthe transmissivity of the electrode plate 9 at the wavelength of 550 nmwas set to 96% (the transmissivity of the single layer of the glasssubstrate 10 was used as a reference) on the display surface portion 16on which the protection layer 5 was formed and thus a relatively largetransmissivity was obtained.

[0081] Therefore, if each of the protection layer 5, lower sideamorphous oxide layer 2 and upper side amorphous oxide layer 4 is formedwith the above-described materials, the composition of the abovematerials and the film thicknesses, the refractive index and opticalfilm thicknesses described above can be attained and the electrode platewith large transmissivity can be obtained.

[0082] Further, since the lower side amorphous oxide layer 2 and upperside amorphous oxide layer 4 for holding the silver-based layer 3therebetween are both formed of amorphous, occurrence of aggregation andslight opaqueness caused by the movement of silver at the interface withthe silver-based layer and a lowering in the transmissivity due to theaggregation and slight opaqueness can be suppressed.

[0083] The reason that each of the upper side amorphous oxide layer andthe lower side amorphous oxide layer has above function is thefollowing.

[0084] An atom of silver is easy to move on the surface with thesilver-based layer. If the silver-based layer under exposing in air isheated at the temperature lied in range of approx. 200 to 300° C., theatoms of the silver diffuses and moves to the interface with thesilver-based layer. The resulting atoms of the silver re-crystallize,grow and finally become clods of the silver. The clods of the silvercauses aggregate and opaque at the interface with the silver-based layerand the reflectance of the silver-based layer is lowered. Note that ifthe interface with the silver-based layer (the respective surfaces ofminute silver crystals before re-crystallization) is planted so-calledcores of some molecular of oxide by sputtering method and the like, thecores act as anchors for suppressing the movement of the atoms ofsilver, prevent the atoms of silver from diffusing to the interface withthe silver-based layer, suppress re-crystallization of the atoms ofsilver at the interface with the silver-based layer and prevent opticalcharacteristic of the silver-based layer from deteriorating.

[0085] Rows of the cores of the oxide planted at the interface with thesilver-based layer are the upper side amorphous oxide layer and thelower side amorphous oxide layer. That is, the upper side amorphousoxide layer and the lower side amorphous oxide layer can be called“anchoring layer” for fixing the movement of the silver at the interfacewith the silver-based layer like “anchor”.

[0086] Therefore, the lower side amorphous oxide layer functions as alower side anchoring layer and the upper side amorphous oxide layerfunctions as an upper side anchoring layer.

[0087] Note that viewing of the reliance, it is preferable thatelectrochemical characteristic (for example, potential of corrode)between the anchoring layer and the silver-based layer is close and theanchoring layer is amorphous or amorphous-like to suppress the diffusingof the silver at the interface with the silver-based layer. Further, itis necessary that the adherence between the anchoring layer and thesilver-based layer is strong.

[0088] Further, it is preferable that the upper/lower side amorphousoxide layer is transparent materials of high resistance to alkali and atleast the upper side amorphous oxide layer is soluble in etchant whichis acid and the like used by etching.

[0089] Note that if the electrode plate of present invention applied fora display device used in a liquid crystal display device is used anelectrode plate for driving liquid crystal, it is preferable that theanchoring layer is made of mixed oxide having basic conductive oxidematerials.

[0090] Further, as shown in FIG. 1, a multi-layered film including thelower side amorphous oxide layer 2, the silver-based layer 3 and theupper side amorphous oxide layer 4 has three layered structure includingthe silver-based layer held between the lower side amorphous oxide layer2 as the anchoring layer and the upper side amorphous oxide layer 4 asthe anchoring layer. However, as will seen later in the thirdembodiment, from the viewing of optical characteristic, it is possiblethat the lower side amorphous oxide layer 2 or the upper side amorphousoxide layer 4 is a multi-layered film including transparent oxide filmlaid on an anchoring layer. Further, it is possible to select the aboveconfigurations of the multi-layered conductive film depending on anapplication of the film.

[0091] Further, since the lower side amorphous oxide layer 2 and upperside amorphous oxide layer 4 for holding the silver-based layer 3therebetween are both formed of amorphous, occurrence of aggregation andslight opaqueness caused by the movement of silver at the interface withthe silver-based layer and a lowering in the reflectance due to theaggregation and slight opaqueness can be suppressed.

[0092] Further, in the terminal portion 17, it is possible to makeelectrical connection with a low electrical resistance to thesilver-based layer 3 via the upper side amorphous oxide layer 4 with athin film thickness. The protection layer 5 on the display surfacepotion 16 can be used as a good insulating protection layer (theprotection layer 5 is used as a film for preventing the electrical shortcircuit with respect to the facing substrate in a liquid crystal displaydevice such as an STN) and the electrode plate with an electrically highreliability can be obtained.

[0093] In this case, the lower side amorphous oxide layer 2 and upperside amorphous oxide layer 4 for holding the silver-based layer 3therebetween are both formed to a film thickness of 10 nm and it isconsidered that the critical value of the film thickness is not largerthan 20 nm in order to attain the same effect. The result is derived bychecking the degree to damage at the interface between the silver-basedlayer and the oxide layer caused by the photolithography process (thetime of etching) from the viewpoint of a change in the connectionresistance in the high temperature and the high humidity and determiningthe film thickness.

[0094] That is, a variation in the connection resistance was observed byvariously changing the film thickness under the general condition (itwas left for 1000 hours in an atmosphere of temperature 70° C. andhumidity 95%) set in the endurance test. As the result, it is found thatthe stability of the connection resistance could be obtained when thefilm thicknesses of the upper side amorphous oxide layer 4 and the lowerside amorphous oxide layer 2 are set to 20 nm or less, and morepreferably, 10 nm or less.

[0095] Further, the total sum of the optical film thickness of theprotection layer 5 (or the underlaid layer 1) and the optical filmthickness of the upper side oxide layer 4 (or the lower side amorphousoxide layer 2) with a film thickness of 10 nm was set to 80.74 nm, butthe same effect can be attained if the total sum is set to 70 nm ormore. The reason is as follows.

[0096] When the film thicknesses of the upper side amorphous oxide layer4 and the lower side amorphous oxide layer 2 holding the silver-basedlayer therebetween are set to 20 nm or less, the reflected lightcomponent from the silver-based layer becomes stronger and thesufficiently large transmissivity cannot be attained. For example, inthe three-layered conductive film having the silver-based layer heldbetween oxide layers with the refractive index of approx. 2, it isdifficult to attain a large transmissivity unless the film thicknessesof the upper side amorphous oxide layer 4 and the lower side amorphousoxide layer 2 are set to approx. 40 to 45 nm.

Second Embodiment

[0097]FIG. 2 is a view showing the schematic structure of an electrodeplate according to a second embodiment of this invention.

[0098] In FIG. 2, the main portion of an electrode plate 19 is formed byforming an underlaid layer 21 formed of SiO₂ with a film thickness of 40nm on a glass substrate 20 (made by NIHON ITAGARASU KABUSHIKI KAISHA, Hcoat product) with a film thickness of 0.7 mm and then sequentiallylaminating a lower side amorphous oxide layer 22 (a lower side anchoringlayer) with a film thickness of 20 nm, a silver-based layer 23 with afilm thickness of 150 nm, and an upper side amorphous oxide layer 24 (anupper side anchoring layer) with a film thickness of 7 nm. The lowerside amorphous oxide layer 22, thin silver-series thin film 23, andupper side amorphous oxide layer 24 form a multi-layered conductivefilm.

[0099] The electrode plate 19 according to the second embodiment is areflective type electrode plate since the film thickness of thesilver-based layer 23 is 150 nm (approx. 100 to 200 nm).

[0100] The electrode plate 19 according to the second embodiment isformed by the following manufacturing process.

[0101] First, the glass plate 20 which is cleaned is inserted into avacuum chamber (sputtering chamber) and a vacuum is drawn.

[0102] Next, the underlaid layer 21 is laminated by the sputteringmethod. Next, the grass substrate 20 is taken out from the vacuumchamber (sputtering chamber), the anneal process (heat treatment) forheating the grass substrate 20 at the temperature of 300° C. for onehour is effected. Next, the grass substrate is inserted into a vacuumchamber (sputtering chamber) and a vacuum is drawn. Next, lower sideamorphous oxide layer 22, silver-based layer 23 and upper side amorphousoxide layer 24 are continuously laminated by the sputtering method.

[0103] Then, the glass plate 20 is taken out from the vacuum chamber anda resist pattern having a preset pattern is formed on the upper sideamorphous oxide layer 24 by the photolithography process. Next, sulfuricacid-series etchant containing nitric acid and iron nitrate by 1 weight% is used as an etching solution to simultaneously remove portions ofthe three layers of the lower side amorphous oxide layer 22,silver-based layer 23 and upper side oxide layer 24 which lie in anexposed portion from the resist pattern by etching.

[0104] Next, after the entire surface of the resist pattern is exposedagain, the resist pattern is removed by use of an organic alkalisolution. After this, the anneal process (heat treatment) for heatingthe substrate at the temperature of 200° C. for one hour is effected toobtain the electrode plate 19 of the second embodiment.

[0105] In the above manufacturing process, the underlaid layer 21 isformed by use of a sputtering target formed of silicon oxide (SiO₂) andhas a function as the alkali barrier layer. Further, the lower sideamorphous oxide layer has a function of an adhesive layer betweenunderlaid layer 21 and the silver-based layer 23.

[0106] The composition of the target used for formation of the lowerside amorphous oxide layer 22 and upper side oxide layer 24 includesindium oxide 77 at %, cerium oxide 20 at % and zinc oxide 3 at % interms of the atomic percentage of metal elements (an oxygen element isnot counted). Further, the composition of the alloy target used forforming the silver-based layer 23 includes silver 98.5 at %, gold 1 at %and copper 0.5 at %.

[0107] The inventors of this invention measured the refractive index ofthe upper-side amorphous oxide layer 24 by use of the same material andcomposition and found that the refractive index was 1.447 at thewavelength of 550 nm and was 1.488 at the wavelength of 430 nm. Theupper side amorphous oxide layer 24 was formed thin with a filmthickness of 7 nm (no laminated layer of oxide is formed thereon) andthe refractive index thereof is smaller than that of the bulk.

[0108] The reflectance of a multi-layered conductive film formed of thesilver-based layer 23 and the upper side amorphous oxide layer 24 wasmeasured by use of the integrating sphere with barium sulfate used as areference and the result showed that the refractive index was 96% at thewavelength of 550 nm and 88% at the wavelength of 430 nm and was thuslarge. Further, the optical film thickness of the upper side amorphousoxide layer 24 with the film thickness of 7 nm and the refractive indexof 1.447 (wavelength 550 nm) was 7×1.447=10.129 nm.

[0109] Depending on the materials of the silver-based layer and theamorphous oxide layers and the surface condition of the ground layer(for example, substrate or the like), the oxide is not formed in theuniform film form but formed in the island form when the film thicknessof the upper side amorphous oxide layer 24 is set in the range of 2 to10 nm, and the film includes voids and the refractive index of the filmis smaller than that of the bulk from the optical viewpoint. As aresult, the reflectance and an optical characteristic are heightened.

[0110] Further, the optical film thickness (the product of the filmthickness and the refractive index) of the upper side amorphous oxidelayer 24 was 10.129 nm, but it is considered that the critical value ofthe film thickness is not larger than 20 nm in order to attain the sameeffect. The result is derived by comparing the reflectance of thereflective type electrode plate using the silver-based layer with thereflectance of the reflective type electrode plate using the aluminumthin film from the viewpoint of optical characteristics and making adetermination based on the comparison result.

[0111] That is, the reflectance of silver is larger than that ofaluminum by approx. 10% and may be a good metal, but the reflectancethereof on the short wavelength side tends to become smaller dependingon the additive amount of an alloy element to silver or the filmthickness of the upper side amorphous oxide layer 24 or the lower sideamorphous oxide layer 22.

[0112] For example, the reflectance of aluminum for light of 430 nm (thewavelength of the blue range) is approx. 85%. Therefore, in order toprovide an electrode plate more excellent than the conventional case, itis necessary to attain the reflectance of approx. 85% or more at thewavelength of 430 nm in the electrode plate of this invention using thesilver-based layer. The inventors of this invention derived from variousstudies that the reflectance of approx. 85% or more could be obtained atthe wavelength of 430 nm if the optical film thickness of the oxidelayer was 20 nm or less in terms of the value of the optical filmthickness which is the product of the film thickness (the unit is nm)and the refractive index.

[0113] However, as described before, in the thin film region, therefractive index of the oxide layer is smaller than that of the bulk.

[0114] The upper side amorphous oxide layer 24 and the lower sideamorphous oxide layer 22 have a function as an anchor fixing themovement of silver at the interface with the silver-based layer, butwhen the film thickness is considered for the function from theviewpoint of high temperature heat resistance, the function can be fullyattained even if the film thickness is approx. 1 nm.

[0115] If the above film thickness is set, the advantage that theetching time is reduced and damage to the interface caused by theetching can be reduced by the reduction in the etching time can beattained, but it is preferable to set the lower limit of the filmthickness to 2 nm or more since the film is somewhat unstable from theviewpoint of the manufacturing process when a variation in the filmthickness at the time of formation of the film and wash-away at the timeof cleaning using an alkali solution or the like are taken intoconsideration.

[0116] In order to check the durability of the optical characteristicsof the electrode plate 19 with the above-described materials, thecomposition of the materials and the thickness and the electrode plate 9according to the first embodiment, the electrode plates were stored for1000 hours in a high-temperature and high-humidity chamber in which thetemperature was set at 70° C. and the humidity was set at 95% andvariations in the optical characteristics were checked. As the result,it was found that variations in the optical characteristics(transmissivity or reflectance) and the adhesive properties of theelectrode patterns were not observed and the reliability (durability)was extremely preferable.

[0117] Therefore, according to the electrode plates 9 and 19, a highlyendurable electrode can be realized.

[0118] Further, in order to check the heat resistance of the electrodeplate 19 with the above-described materials, the composition of thematerials and the thickness and the electrode plate 9 according to thefirst embodiment, the electrode plates 9 and 19 were heated for one hourat the temperature of 250°C. or heated for one hour at the temperatureof 300° C. and the heat resistance of each of the electrode plates 9 and19 was checked. As the result, it was found that a variation in the heatresistance was not observed as in the durability and the electrodeplates had the excellent heat resistance.

[0119] Therefore, according to the electrode plates 9 and 19, a highlyendurable electrode can be realized.

[0120] Further, in order to check the resistance to alkali of theelectrode plate 19 with the above-described materials, the compositionof the materials and the thickness and the electrode plate 9 accordingto the first embodiment, the electrode plates 9 and 19 were dipped in analkali solution (containing NaOH by 1 weight %) at the temperature of40° C. for 10 minutes and the resistance to alkali was checked, but novariation was observed and it was proved that the electrode plate 9according to the first embodiment and the electrode plate 19 had thesufficiently high resistance to alkali in practice.

[0121] Therefore, according to the electrode plates 9 and 19, anelectrode which has the high resistance to alkali can be realized.

[0122] Further, since the lower side amorphous oxide layer 22 and upperside oxide layer 24 for holding the silver-based layer 23 therebetweenare both formed of amorphous, occurrence of aggregation and slightopaqueness caused by the movement of silver at the interface with thesilver-based layer and a lowering in the reflectance of the silver-basedlayer 23 due to the aggregation and slight opaqueness can be suppressed.

[0123] Further, the each connection resistance of the electrode plate 19according to the second embodiment and the electrode plate 9 accordingto the first embodiment was measure by taking the electrical mounting onthe liquid crystal display device such as STN (the evaluation was madeby applying a needle of berylium-copper alloy) and it was found that theconnection resistance was approx. 0.5 to 1Ω and the connectionresistance was lower than that of the transparent electrode (ITO) whichwas normally used.

[0124] Therefore, according to the electrode plate 19 and the electrode9 with the above-described materials, the composition of the materialsand the thickness, the electrodes which are also excellent in theconnection resistance can be obtained.

Third Embodiment

[0125] As shown in FIG. 3, an electrode plate 30 according to a thirdembodiment of this invention has a laminated film 37 formed on a glasssubstrate 31 having an SiO₂ (silicon oxide) layer coated on the surfacethereof and having an alkali barrier function. The laminated film 37 isformed of a lower side amorphous oxide layer 32, silver-based layer 33and upper side oxide layer 34 and the upper side oxide layer 34 is amulti-layered layer having a first amorphous oxide layer 35 (anchoringlayer) and a second amorphous oxide layer 36 laminated on the firstamorphous oxide layer 35. The film thickness of the lower side amorphousoxide layer 32 is set to 25 nm, the film thickness of the silver-basedlayer 33 is set to 15 nm, the film thickness of the amorphous oxidelayer 35 is set to 10 nm, and the film thickness of the second amorphousoxide layer 36 is set to 30 nm. The lower side amorphous oxide layer 32,silver-based layer 33, and upper side oxide layer 34 form amulti-layered conductive film.

[0126] The electronic plate 30 according to the third embodiment is alight transmission type electronic plate since the thin film of thesilver-based layer 33 is 15 nm.

[0127] In this case, the lower side amorphous oxide layer 32 is formedof a mixed oxide material which contained cerium oxide as a mainmaterial and additionally contained niobium oxide by 15 at % in terms ofthe at % (atomic percentage) only of the metal atom which did notinclude the oxygen atom. The amorphous oxide layer 35 is formed of amixed oxide material containing indium oxide, cerium oxide, tin oxideand titanium oxide and the composition thereof contained indium oxide 88at % (atomic percentage), cerium oxide 8.5 at % (atomic percentage),tinoxide 3.0 at % (atomic percentage) and titanium oxide 0.5 at % 8 (atomicpercentage) in terms of the at % (atomic percentage), only of the metalatom which did not include the oxygen atom. The second amorphous oxidelayer 36 is formed of a mixed oxide material which contained ceriumoxide as a main material and additionally contained niobium oxide by 15at % in terms of the at % (atomic percentage) only of the metal atomwhich do not include the oxygen atom. The silver-based layer 33 isformed of a silver alloy having gold and copper added to silver and thecomposition thereof contained silver 98.5 at % (atomic percentage), gold1.0 at % (atomic percentage) and copper 0.5 at % (atomic percentage).

[0128] The electrode plate 30 according to the third embodiment isformed by the following manufacturing process.

[0129] First, the soda glass substrate 31 is subjected to thedegreasing, cleaning and drying process and then put into the sputteringchamber, and a voltage is applied to a mixed oxide (cerium oxide andniobium oxide) target having the above-described composition to form alower side amorphous oxide layer 32 on the soda glass substrate 31 by RF(high frequency) sputtering.

[0130] The atmosphere set in the sputtering chamber is the same as thatset at the time of formation of the lower side oxide thin film in theforth embodiment described later (that is, the gas pressure of the mixedgas of Ar and O₂ was set at 0.35 Pa and the percentage of O₂ was set at10%).

[0131] When the step of forming the lower side amorphous oxide layer 32is completed, discharging and introduction of gas are stopped and avacuum is drawn to the vacuum degree 5×10⁻⁴ Pa in the sputteringchamber.

[0132] Next, Ar gas is introduced into the sputtering chamber to adjustthe gas pressure to 0.4 Pa and a voltage is applied to a silver alloy(silver, gold, copper) target with the above composition to form asilver-based layer 33 by DC (direct current) sputtering.

[0133] When the step of forming the silver-based layer 33 is completed,discharging and introduction of gas are stopped and a vacuum are drawnto the vacuum degree 5×10⁻⁴ Pa in the sputtering chamber.

[0134] Next, a voltage is applied to a mixed oxide (indium oxide andcerium oxide) target with the above composition to form an amorphousoxide layer 35 on the silver-based layer 33 by DC (direct current)sputtering. At this time, the atmosphere set in the sputtering chamberis the same as that set at the time of formation of the upper sideamorphous oxide thin film 44 in the forth embodiment (that is, the mixedgas pressure of Ar and O₂ is set at 0.35 Pa and the percentage of O₂ wasset at 0.75%).

[0135] Next, the soda glass substrate 31 is taken out from thesputtering chamber and a photolithography process from the step ofcoating the photosensitive resin (positive resist) to the step ofseparating the photosensitive resin pattern is effected for the sodaglass substrate 31 in the same manner as in the forth embodiment to formthe silver-based layer 33 and amorphous oxide layer 35 in a presetelectrode pattern.

[0136] At the time of etching, the lower side amorphous oxide layer 32is not etched and remain in the same film form as it was formed.

[0137] Next, the soda glass substrate 31 is put into the sputteringchamber again and the sputtering chamber is evacuated, and then avoltage is applied to a mixed oxide (cerium oxide and niobium oxide)target having the above-described composition to form a second amorphousoxide layer 36 on the substrate 31 by RF (high frequency) sputtering.The RF sputtering is carried out by mask sputtering the second amorphousoxide layer 36 is formed in a predetermined area except the terminalportion of the electrode pattern. Further, the atmosphere set in thesputtering chamber is the same as that set at the time of formation ofthe lower side oxide thin film 42 in the forth embodiment (that is, themixed gas pressure of Ar and O₂ is set at 0.35 Pa and the percentage ofO₂ was set at 10%).

[0138] Next, the substrate on which the second amorphous oxide layer 36is formed is subjected to the drying process at 180° C. for one hour toobtain the electrode plate 30 as shown in FIG. 3.

[0139] During the film formation by sputtering, the substrate is notheated and film formation is continuously effected with the vacuumcondition kept.

[0140] In order to check the electrical stability of the electrode plate30 having the thin films with the above-described materials, thecomposition of the materials and the thicknesses, the electrical shortcircuit between the electrode patterns was checked by use of a wiringtester, but the electrical short circuit between the electrode patternsby the lower side amorphous oxide layer 32 which was not etched andremained was not observed.

[0141] Therefore, with the above structure, the electrode plate withhigh electrical stability can be realized.

[0142] Further, the transmissivity of the electrode plate 30 obtained inthe third embodiment was 70% or more at the wavelength (400 to 700 nm)of the visible region and was sufficiently large and the area resistancewas a low resistance of 2.7 Ω/□.

[0143] Therefore, according to the lower side amorphous oxide layer 32and upper side oxide layer 34 with the above-described materials,composition and thickness, the electrode plate with the largetransmissivity and low resistance can be realized.

[0144] Further, since the lower side amorphous oxide layer 32 and theamorphous oxide layer 35 which hold the silver-based layer 33therebetween are both formed of amorphous, occurrence of aggregation andslight opaqueness caused by the movement of silver at the interface withthe silver-based layer and a lowering in the transmissivity of thesilver-based layer 33 due to the aggregation and slight opaqueness canbe suppressed.

[0145] Further, the amorphous oxide layer 36 according to the thirdembodiment is an amorphous material. However, since the amorphous oxidelayer 36 functions as heightening a transmission by adjustment of therefractive index and a protection layer of the silver-based layer 33,the amorphous oxide layer 36 is not necessarily limited to be amorphous.

[0146] The laminated film 37 obtained in the third embodiment is formedas a transparent electrode, which makes the laminated film 37 to besuppressed the side etching at the time of etching to minimum.

Fourth Embodiment

[0147] As shown in FIG. 4, an electrode plate 40 according to the fourthembodiment of this invention has a laminated film 45 which has a lowerside amorphous oxide layer 42, silver-based layer 43 and upper sideoxide layer 44 sequentially laminated by sputtering on a soda glasssubstrate 41 having an SiO₂ (silicon oxide) layer coated on the surfacethereof and having an alkali barrier function and which is formed into apreset pattern.

[0148] In the fourth embodiment, the film thickness of the lower sideamorphous oxide layer 42 is set to 50 nm, the film thickness of thesilver-based layer 43 is set to 150 nm, and the film thickness of theupper side amorphous oxide layer 44 is set to 8.5 nm.

[0149] Therefore, the electrode plate 40 of the fourth embodiment is areflective type.

[0150] In this case, the lower side amorphous oxide layer 42 is formedof a mixed material which contained cerium oxide as a main material andadditionally contained niobium oxide by 15 at % in terms of the at %(atomic percentage) only of the metal atom which does not include theoxygen atom. The upper side amorphous oxide layer 44 is formed of amixed oxide material containing indium oxide and cerium oxide and thecomposition thereof contained indium oxide 66.7 at % (atomic percentage)and cerium oxide 33.3 at % (atomic percentage) in terms of the at %(atomic percentage) only of the metal atom which does not include theoxygen atom. The silver-based layer 43 is formed of a silver alloyhaving gold and copper added to silver and the composition of the silveralloy contained silver 98.5 at % (atomic percentage), gold 1.0 at %(atomic percentage) and copper 0.5 at % (atomic percentage).

[0151] The electrode plate 40 according to the fourth embodiment isformed by the following manufacturing process. That is, the soda glasssubstrate 41 is subjected to the degreasing, cleaning and drying processand then put into the sputtering chamber, and the sputtering chamber isevacuated.

[0152] When a vacuum is drawn to the vacuum degree 5×10⁻⁴ Pa in thesputtering chamber, Ar (argon) gas and O₂ (oxygen) gas are introducedinto the sputtering chamber to adjust the gas pressure in the sputteringchamber to 0.35 Pa. At this time, O₂ (oxygen) gas in the introduced gasis adjusted to 10% (for example, at the rate of 10 SCCM of theintroduced O₂ gas with respect to introduced Ar gas of 100 SCCM) interms of the percentage of O₂ gas in the introduced gas.

[0153] Next, after the above gas is introduced into the sputteringchamber, a voltage is applied to a mixed oxide (cerium oxide and niobiumoxide) target with the above composition to form a lower side amorphousoxide layer 42 on the substrate 41 by RF (high frequency) sputtering.

[0154] When the step of forming the lower side amorphous oxide layer 42is completed, discharging and introduction of gas are stopped and avacuum is drawn to adjust the gas pressure to the vacuum degree 5×10⁻⁴Pa in the sputtering chamber.

[0155] Next, Ar gas is introduced into the sputtering chamber to adjustthe gas pressure to 0.4 Pa and a voltage is applied to a silver alloy(silver, gold, copper) target with the above composition to form asilver-based layer 43 by DC (direct current) sputtering.

[0156] When the step of forming the silver-based layer 43 is completed,discharging and introduction of gas are stopped and a vacuum is drawn toadjust the gas pressure to the vacuum degree 5×10⁻⁴ Pa in the sputteringchamber.

[0157] Next, Ar (argon) gas and O₂ (oxygen) gas are introduced into thesputtering chamber to adjust the gas pressure in the sputtering chamberto 0.35 Pa. At this time, the amount of O₂ (oxygen) gas in theintroduced gas is adjusted to 0.75% (for example, at the rate of 0.75SCCM of the introduced O₂ gas with respect to introduced Ar gas of 100SCCM) in terms of the percentage of O₂ gas in the introduced gas.

[0158] Next, after the above gas is introduced into the sputteringchamber, a voltage was applied to a mixed oxide (indium oxide and ceriumoxide) target with the above composition to form an upper side amorphousoxide layer 44 by DC (direct current) sputtering and thus athree-layered laminated film 45 is formed.

[0159] During the film formation, the substrate 41 is not heated andfilm formation is continuously effected with the vacuum condition kept.

[0160] According to the above-described materials, composition andthicknesses, the light reflectance of the laminated film 45 is 88% ormore at the wavelength (400 to 700 nm) of the visible region and issufficiently large. Further, the area resistance of the laminated film45 is 0.28 Ω/□ and the electrode plate of low resistance can berealized.

[0161] Next, the manufacturing method for subjecting the laminated film45 obtained in the above manufacturing process to the followingphotolithography process to form a preset pattern is explained.

[0162] First, photosensitive resin (positive resist) is coated to a filmthickness 1 μm on the laminated film 45 obtained in the abovemanufacturing process by use of a spinner and then a dry process iseffected at 90° C. for 20 minutes in an oven.

[0163] Next, after patterning exposure is effected on the photosensitiveresin by use of an exposure device using an exposure photomask having apreset pattern, the development is effected by use of an alkalideveloping solution (potassium hydroxide 10 weight %). As a result, aportion of the photosensitive resin subjected to the patterning exposureis dissolved and removed and a photosensitive resin pattern is formed ina preset reflection film portion.

[0164] After the development, a dry process is effected again at 90° C.for 20 minutes in the oven.

[0165] Next, an etching solution containing a mixture of sulfuric acid,nitric acid and acetic acid is used for etching the laminated film andthe etching process is effected by dipping the laminated film in theetching solution at the liquid temperature 40° C. for approx. 30 seconds(that is, the portion of the laminated film exposed from thephotosensitive resin pattern was dissolved and removed by etching). Atthe time of etching, the lower side amorphous oxide layer 42 is notetched out and remained in the same film form as it was formed.

[0166] After light is applied to the whole portion of the substrateafter etching, the photosensitive resin pattern is separated by use ofan alkali separating solution (potassium hydroxide 1 weight %).

[0167] Next, the substrate is subjected to the drying process at 180° C.for one hour to obtain the electrode plate 45 (reflection electrode) ofa preset pattern.

[0168] The side etching to the laminated film 45 obtained in thephotolithography process is suppressed to minimum at the time of etchingand a gap (a distance between the adjacent electrodes) between theelectrode patterns formed by etching could be set to such a small valueas approx. 6 μm.

[0169] According to the above manufacturing method, the width of theelectrode pattern can be enlarged by an amount by which the amount ofthe side etching can be reduced and light can be effectively reflected.

[0170] Further, the electrode plate 40 obtained in the fourth embodimentis tested by use of the wiring tester to check the electricalshort-circuit between the electrode patterns, but the electrical shortcircuit between the electrode patterns by the lower side amorphous oxidelayer 42 which is not etched and remained is not observed and theelectrode plate 40 with high electrical stability can be realized.

[0171] Further, since the lower side amorphous oxide layer 42 and upperside oxide layer 44 for holding the silver-based layer 43 therebetweenare both formed of amorphous, occurrence of aggregation and slightopaqueness caused by the movement of silver at the interface with thesilver-based layer, and a lowering in the reflectance of thesilver-based layer 43 due to the aggregation and slight opaqueness canbe suppressed.

Fifth Embodiment

[0172] Like the fourth embodiment, an electrode plate 40 according tothe fifth embodiment of this invention has a laminated film 45 which hasa lower side amorphous oxide layer 42, silver-based layer 43 and upperside amorphous oxide layer 44 sequentially laminated by sputtering on asoda glass substrate 41 having an SiO₂ (silicon oxide) layer coated onthe surface thereof and which is formed into a preset pattern.

[0173] The schematic view of the electrode plate of the fifth embodimentis the same as that of FIG. 4, but the thicknesses of the layers aredifferent and the film thickness of the lower side amorphous oxide layer42 was set to 50 nm, the film thickness of the silver-based layer 43 isset to 150 nm and the film thickness of the upper side amorphous oxidelayer 44 is set to 3.5 nm.

[0174] Also, the electrode plate 40 of the fifth embodiment is areflective type.

[0175] The lower side amorphous oxide layer 42 is formed of a mixedoxide material which contains cerium oxide as a main material andadditionally contained niobium oxide by 15 at % in terms of the at %(atomic percentage) only of the metal atom which does not include theoxygen atom. The upper side oxide layer 44 is formed of a mixed oxidematerial containing indium oxide, cerium oxide, tin oxide and titaniumoxide and the composition thereof contains indium oxide 88 at % (atomicpercentage), cerium oxide 8.5 at % (atomic percentage),tin oxide 3.0 at% (atomic percentage) and titanium oxide 0.5 at % in terms of the at %(atomic percentage) only of the metal atom which does not include theoxygen atom. Further, the silver-based layer 43 is formed of a silveralloy having gold and copper added to silver and the composition of thesilver alloy contained silver 98.5 at % (atomic percentage), gold 1.0 at% (atomic percentage) and copper 0.5 at % (atomic percentage).

[0176] The electrode plate 40 according to the fifth embodiment isformed by the following manufacturing process. That is, the soda glasssubstrate 41 is subjected to the degreasing, cleaning and drying processand then put into the sputtering chamber.

[0177] The internal portion of the sputtering chamber used in the fifthembodiment is divided into three continuous chambers. In order toprevent contaminations occurring during the film formation from givingan influence on the process in the adjacent chamber, the chambers arearranged with a preset space from one another and a shielding andexhaust measure is taken. After the soda glass substrate 41 is put intothe sputtering chamber, a vacuum is drawn in the sputtering chamber, andAr gas is introduced when the vacuum degree reached 5×10⁻⁴ Pa and thegas pressure in the sputtering chamber is adjusted to 0.4 Pa.

[0178] The soda glass substrate 41 put into the sputtering chamber iscarried by a carriage tray (not shown) and moved at a constant speed ineach chamber of the sputtering chamber. At this time, the lower sideamorphous oxide layer 42, silver-based layer 43 and upper side amorphousoxide layer 44 are sequentially formed in the respective chambers.

[0179] When the substrate 41 passes through the first chamber of thesputtering chamber, a voltage is applied to a mixed oxide (cerium oxideand niobium oxide) target having the above-described composition to forma lower side amorphous oxide layer 42 by RF (high frequency) sputtering.Likewise, when the substrate 41 passes through the second chamber, avoltage is applied to a silver alloy (silver, gold and copper) targetwith the above composition to form a silver-based layer 43 by DC (directcurrent) sputtering. Next, when the substrate 41 passes through thethird chamber, a voltage is applied to a mixed oxide (indium oxide andcerium oxide) target having the above-described composition to form anupper side amorphous oxide layer 44 by DC (direct current) sputtering.At the time of formation of the oxide layer, O₂ gas is introduced intothe first and third chambers in addition to Ar gas and the rate of O₂gas introduced into the first chamber is 7% (the rate of 7 SCCM ofintroduced O₂ gas with respect to introduced Ar gas of 100 SCCM) and therate of O₂ gas introduced into the third chamber is 0.75% (the rate of0.75 SCCM of introduced O₂ gas with respect to introduced Ar gas of 100SCCM).

[0180] During formation of the film on the substrate 41, the glasssubstrate 41 is not heated and the substrate 41 is subjected to thebaking process at 180° C. for one hour after the laminated film isformed.

[0181] The three-layered laminated film 45 obtained in the fifthembodiment is formed as a reflection film, the light reflectance thereofis 90% or more and sufficiently large at the wavelength (400 to 700 nm)of the visible region, and the area resistance is as low as 0.27 Ω/□.

[0182] Therefore, according to the electrode plate 40 having the thinfilms with the above-described materials, the composition of thematerials and the thicknesses, the electrode plate with the largereflectance and low resistance can be realized.

[0183] Further, since the lower side amorphous oxide layer 42 and theupper side amorphous oxide layer 44 which hold the silver-based layer 43therebetween are both formed of amorphous, occurrence of aggregation andslight opaqueness caused by the movement of silver at the interface withthe silver-based layer and a lowering in the reflectance of thesilver-based layer 43 due to the aggregation and slight opaqueness canbe suppressed.

[0184] Further, since the lower side amorphous oxide according to thethird, forth, fifth embodiment is insulation, patterning to the lowerside amorphous oxide is needless, which makes easy to form patterns.

[0185] Therefore, according to the electrode plate with the abovematerials, the composition of the materials and the thickness, atransparent electrode plate with the large transmissivity or thereflectance and low resistance can be realized.

[0186] Further, in this invention, since the insulated film can belaminated being adjusted to attain an optical characteristic, theconventional process for forming a insulated film called overcoat isneedless, which can make the manufacturing process to be simple.

[0187] As described above, this invention has been explained withreference to the embodiments, but this invention is not limited to theabove embodiments and, for example, this invention can be variouslymodified without departing from the technical scope thereof as follows.

[0188] (1) The lower side amorphous oxide layers in the third, fourth,fifth and sixth embodiments were each formed of a mixed oxide materialwhich contained cerium oxide as a main material and additionallycontained niobium oxide by 15% in terms of the at % (atomic percentage)only of the metal atom which did not include the oxygen atom. Oxideadded to cerium oxide is not limited to niobium, but oxides of metals inthe groups 3A, 4A, 5A of the periodic table may be used. Particularly,it is preferable to add one or more types of oxides selected from agroup of ytrium oxide, zirconium oxide, niobium oxide, hafnium oxide,tantalum oxide and tungsten oxide.

[0189] The lower side amorphous oxide layer with the aboveconfigurations has good adherence for the silver-based layer and alkalibarrier effect. Further, the lower side amorphous oxide layer is enoughstable not to be etched by etching solution used in photolithographyprocess and at the time of patterning, and remains in the same film formas it was formed. As a result, if there is no under-laid layer between asubstrate and multi-layered conductive film, migration of alkali metalto the silver-based layer is prevented. Further, if the lower sideamorphous oxide layer remains in the film form, the lower side amorphousoxide layer does not cause the electrical short circuit to the electrodepatterns due to having no conductivity.

[0190] With the above configuration, the same effect can be attained.

[0191] (2) When the electrode plate according to this invention is usedfor a liquid crystal or the like, the materials of the upper sideamorphous oxide layer 4, upper side amorphous oxide layer 24, upper sideamorphous oxide layer 44, amorphous oxide layer 35, lower side amorphousoxide layer 2 and lower side amorphous oxide layer 22 may be changed tothe following material from the viewpoint of the refractive index andconductivity.

[0192] That is, if it is desired to obtain oxide of the small refractiveindex, for example, SiO₂, MgO, Al₂O₃, GeO₂, Bi₂O₃ may be used and if itis desired to obtain oxide of the large refractive index, for example,TiO₂, CeO₂, ZrO₂, HfO₂, Nb₂O₅, Ta₂O₅ may be used. Further, as theconductive oxide material, In₂O₃, SnO₂, ZnO may be used, for example.

[0193] Therefore, an oxide material other than the above oxide materialsor a mixed oxide material selectively and mixedly containing two or moretypes of the above oxide materials or the like in which the number ofoxygen elements added thereto is adjusted may be used to form theamorphous oxide layer, upper side amorphous oxide layer or lower sideamorphous oxide layer.

[0194] If a mixed oxide material having In₂O₃ or ZnO used as thesubstrate material is used, the etching process can be easily effected.

[0195] Further, the precision of the configuration of the electrodepattern formed on the electrode plate and the reliability of theelectrode according to this invention can be further enhanced by addinga small amount of oxide material such as ZnO or MgO which is easilydissolved into acid to the above mixed oxide material so as to set theoxidation-reduction potential of the mixed oxide material closer to thatof the silver-based layer.

[0196] Further, a layer with the large refractive index may be insertedinto the central portion in the thickness direction of the silver-basedlayer used for the electrode plate according to this invention from theviewpoint of the refractive index. In the case of a transmission typeconductive film, a conductive film with the smaller reflectance can beobtained by inserting a layer with the large refractive index betweenthe silver-based layers. At this time, the transmissivity may beimproved in some cases.

[0197] (3) In all of the above embodiments, the transparent substratewas used as the substrate used for the electrode plate for displaydevice according to this invention. However, the substrate is notnecessary transparent and may be a substrate which is colored in white,black or other color according to the application of the display device.

[0198] The substrate itself may be a substrate on which an electriccircuit is formed, a silicon wafer substrate on which a solar battery isformed, or a heat-resistant organic film or a substrate on whichsemiconductor elements of amorphous silicon, polysilicon or MIM (diodeelements) are formed.

[0199] Further, it is possible to directly or indirectly form apolarization element, diffraction grating, hologram, light scatteringfilm, λ/4 wavelength plate, phase difference film, micro-lens, colorfilter or the like on the substrate.

[0200] (4) The protection layer in the above embodiments is formed ofoxide which is highly resistant to chemical and has a high insulatingproperty from the viewpoint of reliability (durability). However,nitride, organic resin, fluororesin, Teflon resin, silicon resin or thelike may be used other than the above oxide material, or a coating filmhaving a transparent pigment mixed in the above materials may be used.Further, a reflection preventing film or water repellent layer can beformed on the protection layer from the viewpoint of reliability(durability).

[0201] In a case where the electrode plate of this invention is used forsolar battery (in this case, a semiconductor element of amorphoussilicon, for example, is formed on the substrate), the protection layermay be formed sufficiently thick to attain high reliability (highdurability).

[0202] Further, the protection layer may be formed by use of the sol-gelmethod which is used for means for forming a layer which is generallycalled an “overcoat” on the liquid crystal substrate.

[0203] When the protection layer is required to have a large dielectricfactor for driving the crystal such as TFT, ferroelectric crystal orantiferroelectric crystal, the protection layer may be formed of amaterial with large dielectric factor.

[0204] (5) The silver-based layer included in the electrode plateaccording to the first, second, third, forth and fifth embodiment formsa preferable reflection electrode when the film thickness thesilver-based layer is set to approx. 100 to 200 nm or more and forms apreferable transparent electrode when the film thickness thereof is setin a range of approx. 7 to 25 nm. However, the film thickness thereof isnot limited in the above ranges. If the silver-based layer forms asemi-reflection electrode or semi-transparent electrode when the filmthickness thereof is set to approx. 5 to 100 nm. The each of thetransparent component and the reflection component has the same effectof the present invention.

[0205] Note that, generally speaking, the electrode plate is apreferable reflective electrode plate when the reflectance of theelectrode plate is more than 70% and is a preferable transparentelectrode when the transmissivity of the electrode plate is more than88% at the wavelength (400 to 700 nm) of the visible region.

[0206] As described above, according to this invention, an electrodeplate having a transmission type or reflective type conductive film andhaving an excellent optical characteristic (transmissivity,reflectance), low electrical connection resistance, good patterningconfiguration, and high stability can be realized.

1. An electrode plate for display device comprising: a substrate; and amulti-layered conductive film, wherein said multi-layered conductivefilm includes a silver-based layer, a lower side amorphous oxide layerformed of an amorphous or amorphous-like material for suppressingmovements of silver atoms at an interface with said silver-based layer,and an upper side amorphous oxide layer formed of an amorphous oramorphous-like material for suppressing movements of silver atoms at aninterface with said silver-based layer and at least a film thickness ofsaid upper side amorphous oxide layer is not larger than 20 nm.
 2. Theelectrode plate for display device according to claim 1 , wherein saidupper side amorphous oxide layer comprises an oxide layer of whichoptical film thickness defined as a product of a film thickness and arefractive index is not larger than 20 nm.
 3. The electrode plate fordisplay device according to claim 1 , which further comprises aprotection layer formed on said upper side amorphous oxide layer and inwhich a sum of the optical film thicknesses of said upper side amorphousoxide layer and said protection layer is not less than 70 nm.
 4. Theelectrode plate for display device according to claim 1 , furthercomprising a protection layer formed on said upper side amorphous oxidelayer, said protection layer being an oxide layer having a refractiveindex not larger than that of said upper side amorphous oxide layer. 5.The electrode plate for display device according to claim 1 , whereinsaid lower side amorphous oxide layer has an underlaid layer formed ofan oxide layer having a refractive index not larger than that of thelower side amorphous oxide layer.
 6. The electrode plate for displaydevice according to claim 1 , wherein said lower side amorphous oxidelayer is formed of a mixed oxide material which contains cerium oxide asa main material and additionally contains at least one oxide materialselected from a group of ytrium oxide, zirconium oxide, niobium oxide,hafnium oxide, tantalum oxide and tungsten oxide.
 7. The electrode platefor display device according to claim 6 , wherein at least niobium oxideis selected to be added to the cerium oxide which is the main materialof said lower side oxide layer.
 8. The electrode plate for displaydevice according to claim 6 , wherein said lower side amorphous oxidelayer formed of an amorphous or amorphous-like material is formed of amixed oxide which contains at least niobium oxide mixed with ceriumoxide.
 9. An electrode plate for display device comprising: a substrate;and a multi-layered conductive film; wherein said multi-layeredconductive film includes a lower side amorphous oxide layer formed of anamorphous or amorphous-like material for suppressing a movement ofsilver atom at an interface with said silver-based layer, a silver-basedlayer, and an upper side oxide layer and said upper side oxide layerincludes an oxide layer and an amorphous oxide layer formed of anamorphous or amorphous-like material for suppressing a movements ofsilver atoms at an interface with said silver-based layer and a filmthickness of said upper side amorphous oxide layer is not larger than 20nm.
 10. The electrode plate for display device according to claim 9 ,wherein an optical film thickness defined as a product of the filmthickness and a refractive index of said amorphous oxide layer includedin said upper side oxide layer is not larger than 20 nm.
 11. Theelectrode plate for display device according to claim 9 , which furthercomprises a protection layer formed on said upper side oxide layer andin which a sum of the optical film thicknesses of said upper side oxidelayer and said protection layer is not less than 70 nm.
 12. Theelectrode plate for display device according to claim 9 , furthercomprising a protection layer formed on said upper side oxide layer,said protection layer being an oxide layer having a refractive index notlarger than that of said amorphous oxide layer included in said upperside oxide layer.
 13. The electrode plate for display device accordingto claim 9 , wherein said lower side amorphous oxide layer has anunderlaid layer formed of an oxide material having a refractive indexnot larger than that of the lower side amorphous oxide layer.
 14. Theelectrode plate for display device according to claim 9 , wherein saidlower side amorphous oxide layer is formed of a mixed oxide materialwhich contains cerium oxide as a main material and additionally containsat least one oxide material selected from a group of ytrium oxide,zirconium oxide, niobium oxide, hafnium oxide, tantalum oxide andtungsten oxide.
 15. The electrode plate for display device according toclaim 14 , wherein at least niobium oxide is selected to be added to thecerium oxide which is the main material of said lower side amorphousoxide layer.
 16. The electrode plate for display device according toclaim 14 , wherein said lower side amorphous oxide layer formed of anamorphous or amorphous-like materials is formed of a mixed oxide whichcontains at least niobium oxide mixed with cerium oxide.
 17. Theelectrode plate for display device according to any one of claims 1, 6,9 and 14, wherein said silver-based layer is a silver alloy containingat least one metal selected from a group of platinum, palladium, gold,copper and nickel added to silver by not larger than 3 at % (atomicpercentage).
 18. A method for manufacturing an electrode plate fordisplay device comprising the following steps of: forming amulti-layered conductive film on a substrate, the multi-layeredconductive film comprising a lower side amorphous oxide formed ofamorphous or an amorphous-like oxide, an upper side amorphous oxideformed of an amorphous or amorphous-like oxide and a silver-based layerwhich held between the lower side amorphous oxide layer and the upperside amorphous oxide layer, a film thickness of the upper side amorphousoxide layer being not larger than 20 nm; forming an electrode bypatterning the oxide layers together with the silver-based layer; andforming a protection layer on the electrode, a film thickness of theprotection layer being adjusted to attain an optimum opticalcharacteristic as the electrode.
 19. The method for manufacturing theelectrode plate for display device according to claim 18 , wherein saidstep of forming the protection layer comprises a step of forming theprotection layer formed of an electrically insulating material on theelectrode with a sufficiently large film thickness for protection in aportion other than an electrical connection portion of the electrode.20. The method for manufacturing the electrode plate for display deviceaccording to claim 18 , wherein said electrode forming step usesa,photolithography method using a photoresist, the photoresist of theelectrode portion for electrical connection is left behind when thephotoresist is selectively removed after the electrode pattern is formedby use of the process of the photolithography method, the photoresistleft behind is used as mask for forming the protection layer, and thenthe photoresist is removed to expose the electrode portion forelectrical connection from the protection layer.
 21. The method formanufacturing the electrode plate for display device according to claim18 , wherein said pattern processing step of effecting the patterningprocess is a mask sputtering method.
 22. A method for manufacturing anelectrode plate for display device comprising the following steps:forming a lower amorphous oxide layer formed of an amorphous oramorphous-like material; forming a silver-based layer on the lower oxidelayer; and forming an upper amorphous oxide layer formed of an amorphousor amorphous-like material and having a film thickness not larger than20 nm on the silver-based layer.